The actual bullet weight is less important than the burn-rate of the powder.
It’s my understanding M2 Ball ammo is loaded with IMR4895 powder. IMR4064 was actually preferred ballistically, but its grain size/shape made it impractical for machine measuring/loading. My Garand seems to be a little more accurate using 4064, but I measure my powder charges by hand.
If factory ammo with 150-grain bullets has powder that burns at least as fast as IMR4895/4064, it’s suitable for use in a Garand with a standard non-venting gas-cylinder plug.
My suggestion would be to either use mil-surplus ammo or load your own.
Thanks. I need to make time to mess with the adjustable plug.
FReegards